1. Field of Invention
The present invention relates to a crosshead for producing a stripe electric wire in which, when a conductor is covered with a synthetic resin of the ground color in a wire cover extrusion line, colored resins of a color different from the ground color are supplied in a stripe manner from stripe sub extruders, and more particularly to a crosshead in which a mixed color area (color change loss) that is produced when the color of a colored resin covering in a stripe manner, or that of a skin layer colored resin is changed can be reduced.
2. Related Art
Usually, an electric wire has a structure in which the outside of a conductor is covered with an insulator of a synthetic resin. In order to prevent erroneous connection from occurring, such an electric wire is configured as a stripe electric wire in which the insulator is covered in a strip-like manner with a resin of a color different from the ground color so as to identify the wire. In such a stripe electric wire, the stripe coloring on the insulator is performed by using a stripe sub extruder 13, a covering resin supplied from a ground color main extruder 9 is used as a ground color resin, and the covering resin is covered with a colored covering resin in a stripe manner.
Conventionally, the stripe electric wire is produced by using a crosshead such as shown in FIG. 7.
The crosshead body 2 of the crosshead 1 is formed into a cylindrical shape. A cylindrical nipple 4 in which the tip end is tapered and a strand conductor 3 runs through the center is fitted into the crosshead body 2 so as to maintain a predetermined gap between the nipple and the inner face of the crosshead body 2. An insert mold 5 which is formed into a cylindrical shape is fittingly attached to the tip end portion of the crosshead body 2. A hole through which a covered wire 6 in which the strand conductor 3 is covered with a resin is to run is formed in the center of the insert mold 5. A die 7 which is tapered toward the center is fixedly attached to the mold. The die 7 and the nipple 4 are placed at the same center.
A ground color resin supply path 8 is opened in the crosshead body 2. A ground color main extruder 9 is attached to the body so as to communicate with the ground color resin supply path 8. A ground color resin is supplied from the ground color main extruder 9 into the crosshead body 2 via the ground color resin supply path 8. The reference numeral 10 denotes a seal for attaching the ground color main extruder 9 to the crosshead body 2, and 11 denotes a switch cock for, when the color of the ground color resin from the ground color main extruder 9 is to be changed, stopping the supply of the resin therefrom.
A stripe resin supply path 12 is opened in the crosshead body 2. A stripe sub extruder 13 is attached to the body so as to communicate with the stripe resin supply path 12. A colored resin for a stripe is supplied from the stripe sub extruder 13 into the crosshead body 2 via the stripe resin supply path 12.
The reference numeral 14 denotes a seal for attaching the stripe sub extruder 13 to the crosshead body 2, and 15 denotes a switch cock for, when the color of the colored resin from the stripe sub extruder 13 is to be changed, stopping the supply of the resin therefrom.
The switch cock 15 is used for stopping the supply of the stripe covering resin to the crosshead body 2, and discharging a part of the stripe covering resin of a new color which is continuous to that of the old color that has been used before the color change. In the switch cock 15, in order to smoothly supply the colored resin to the crosshead body 2, a heater is internally disposed to heat the colored resin to an appropriate temperature.
The switching by means of the switch cock 15 is performed in the following manner. The supply route from the stripe sub extruder 13 to the crosshead body 2 is changed to a discharge route from the stripe sub extruder 13 to the outside by an adequate method. In the case where the switching of the switch cock 15 is to be conducted, before the switching of the switch cock 15, the production line is stopped, and a hopper storing a coloring material is switched to another one so that the colored stripe covering resin to be supplied to the stripe sub extruder 13 is replaced with a resin of another color. Thereafter, the switch cock 15 is switched over from the supply route from the stripe sub extruder 13 to the crosshead body 2, to the discharge route from the stripe sub extruder 13 to the outside. As a result of the switching of the switch cock 15, the stripe colored resin which has been extruded by the stripe sub extruder 13 is discharged through a discharge port of the switch cock 15.
A stripe electric wire is produced by using the thus configured crosshead 1 in the following manner. The ground color resin supplied from the ground color main extruder 9 is sent via the ground color resin supply path 8 to the tip end of the nipple 4 with passing through the gap between the inner peripheral face of the crosshead body 2 and the outer peripheral face of the nipple 4. The surface of the strand conductor 3 is covered with the resin at a predetermined thickness by means of the tapered tip end portion of the crosshead body 2 and the tapered portion of the die 7. When the surface of the strand conductor 3 is to be covered with the resin at the predetermined thickness, the stripe colored resin is extruded from the stripe sub extruder 13 with passing through the stripe resin supply path 12, into the ground color resin passing through the gap between the inner peripheral face of the crosshead body 2 and the outer peripheral face of the nipple 4, so as to be longitudinally added in a stripe manner. The colored resin is then sent together with the ground color resin, and the surface of the strand conductor 3 is covered with the colored resin in a stripe manner by means of the tapered tip end portion of the crosshead body 2 and the tapered portion of the die 7.
In the production of a stripe electric wire by using the crosshead 1, the color of the stripe is sometimes changed although the ground color resin is not changed. In this case, the ground color resin is continued to be supplied from the ground color main extruder 9. In the stripe sub extruder 13, by contrast, the running of the strand conductor 3 is temporarily stopped, the supply of the colored resin from the stripe sub extruder 13 to the crosshead body 2 is temporarily stopped, and the color of the colored resin in the stripe sub extruder 13 is changed. When the color change of the colored resin in the stripe sub extruder 13 is performed, the covering resin of the old color which is used before the color change is discharged through the discharge port (not shown) of the switch cock 15. When the discharge of the covering resin of the new color is checked and it is judged that the output of the covering resin of the new color is completely attained, the switch cock 15 is returned to the resin supplying position to restart the extrusion covering on the strand conductor 3. When the new colored resin is supplied from the thus configured stripe sub extruder 13, the colored resin of the old color remains in the stripe resin supply path 12 or the like, and hence the colored resin of the old color is initially supplied, and the colored resin for forming a stripe which is supplied as a result of the color changing is then extruded in succession and continuously with the colored resin of the old color. The colored resin of the old color is mixed with that of the new color, and then replaced with that of the new color.
The resin which is initially discharged from the discharge port of the switch cock 15 is the colored resin of the old color which is used before the color change, and after a short time a resin in which the stripe covering resin of the old color is mixed with that of the new color is discharged. After a further short time elapses, only the stripe covering resin of the new color is discharged. At the timing when the discharge of only the stripe colored resin of the new color is checked, the switch cock 15 is switched over to change the discharge route from the stripe sub extruder 13 to the outside, to the supply route from the stripe sub extruder 13 to the crosshead body 2. As a result of the switching of the switch cock 15, the stripe colored resin of the new color is supplied to the crosshead body 2. At the same time when the switch cock 15 is switched over, the production line is restarted. In this way, the switching from the stripe covering resin of the old color to that of the new color is performed.
However, the conventional crosshead has the following problems. In the case where the color of the stripe colored resin with which the surface of the strand conductor 3 is covered is to be changed, the hopper storing a coloring material is switched to another one to change the colored resin, the covering resin of the old color which has been used before the color change and which remains in the stripe sub extruder is then discharged, and it is checked that the covering resin of the new color is discharged. Therefore, the changing operation requires much labor, and, when the switching by means of the switch cock is delayed, the covering resin is lost in a larger amount. Particularly, the resin of the old color remains in the range xe2x80x9cfrom the switch cock to the insert mold,xe2x80x9d and a mixed color area is produced in a subsequent extrusion of the resin of the next color, with the result that a color change loss is caused.
It is an object of the invention to prevent a mixed color area from being produced in a process of changing from the old color to the next color, thereby eliminating a color change loss (color failure of an electric wire).
In order to attain the object, the crosshead of a first aspect of the invention is configured so that a ground color main extruder which supplies a ground color resin that is to cover a strand conductor is disposed, plural stripe sub extruders which supply a colored resin in a strip-like manner in a longitudinal direction of the strand conductor simultaneously with extrusion of the ground color resin are disposed, insert molds are multiply disposed, and, while alternatingly switching over the stripe sub extruders each time when a colored resin to be supplied is changed, a colored resin of a predetermined color is supplied through a path which is disposed for each of the stripe sub extruders.
According to the first aspect of the invention configured as described above, production of a mixed color area in a process of changing from the old color to the next color can be largely reduced, and a color change loss (color failure of an electric wire) can be greatly decreased.
In order to attain the object, the crosshead of a second aspect of the invention is configured so that stripes are formed are formed by pairing symmetrical positions on an outer periphery of a covered wire, and separating the positions by a predetermined angle for each of the stripe sub extruders.
According to the second aspect of the invention configured as described above, the resin pressure in the crosshead can be uniformalized, and a stripe electric wire in which the stripe is positioned in balance can be produced.
In order to attain the object, the crosshead of a third aspect of the invention is configured so that one or plural skin layer sub extruders which form a skin layer on a covered wire covered with an inner layer resin by the ground color main extruder are attached to the crosshead, and a skin layer insert mold for forming the skin layer is singly or multiply disposed.
According to the third aspect of the invention configured as described above, an inner layer resin can be thinly covered with a resin of a preferred color so that the ground color of the covered electric wire can be freely changed without being affected by the color of the inner layer resin.
In order to attain the object, the crosshead of a fourth aspect of the invention is configured so that, in middles of supply paths through which the colored resins of the stripe sub extruders are supplied to the insert molds, switch cocks which allow and stop the supplies of the colored resins from the stripe sub extruders to the insert molds are respectively disposed, and resin discharge paths which respectively elongate from positions where the switch cocks are attached, and which are opened to an outside are disposed.
According to the fourth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.
In order to attain the object, the crosshead of a fifth aspect of the invention is configured so that, in middles of supply paths through which colored resins of the skin layer sub extruders are supplied to the skin layer insert molds, switch cocks which allow and stop the supplies of the colored resins from the skin layer sub extruders to the skin layer insert molds are respectively disposed, and resin discharge paths which respectively elongate from positions where the switch cocks are attached, and which are opened to an outside are disposed.
According to the fifth aspect of the invention configured as described above, during an operation of changing the color of the colored resin for the skin layer, the colored resin of the old color which remains in the range from the skin layer sub extruder to the switch cock can be surely discharged to the outside, and hence it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.
In order to attain the object, the crosshead of a sixth aspect of the invention is configured so that each of the switch cock is a cock which is formed into a columnar shape, and in which a resin path that radiately communicates with a center is formed, and a discharge path elongates from a position where the resin path is formed, toward a center axis and so as not to communicate with the resin path, and is opened in an end portion.
According to the sixth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin or that of changing the color of the colored resin for the skin layer, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.
In order to attain the object, the crosshead of a seventh aspect of the invention is configured so that, when the colored resins are to be supplied from the stripe sub extruders to the insert molds, the switch cocks cause sub-extruder supply paths through which the colored resins from the stripe sub extruders are supplied, to communicate with insert mold supply paths through which the colored resins are supplied to the insert molds, and, when the supplies of the colored resins from the stripe sub extruders are to be stopped, cause the sub-extruder supply paths through which the colored resins from the stripe sub extruders are supplied, to communicate with the resin discharge paths, and the insert mold supply paths to communicate with the discharge paths.
According to the seventh aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.
In order to attain the object, the crosshead of an eighth aspect of the invention is configured so that, when the supplies of the colored resins from the stripe sub extruders are stopped, resins remaining in the sub-extruder supply paths elongating from the stripe sub extruders to the switch cocks are discharged to the outside through the resin discharge paths, by extruding the colored resins of a new color supplied from the stripe sub extruders, and resins remaining in the insert mold supply paths elongating from the switch cocks to the insert molds are discharged by a pressure of the ground color resin extruded from the ground color main extruder into the crosshead body, to the outside through the discharge paths of the switch cocks.
According to the eighth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.